Mills Ch22 Stomach

22

Stomach David A. Owen

EMBRYOLOGY AND POSTNATAL DEVELOPMENT  601 GROSS MORPHOLOGIC FEATURES  601

ULTRASTRUCTURE  608 GASTRIC FUNCTION  608 SPECIAL TECHNIQUES AND PROCEDURES  609 AGE CHANGES  609 ARTIFACTS  609 DIFFERENTIAL DIAGNOSIS  609 Metaplasia  612 SPECIMEN HANDLING  613 REFERENCES  613

Blood Supply  602 Nerve Supply  602 Lymphatics  603 GENERAL HISTOLOGIC FEATURES  603 Surface Epithelium  604 Cardiac and Pyloric Mucosa  604 Oxyntic Gland Mucosa  605

Endocrine Cells  606 Lamina Propria  607 Submucosa  607 Muscular Components  607

the esophagus several centimeters below the level of the dia- phragm. At its distal end, it merges with the duodenum, just to the right of the midline. The stomach is extremely distensible, and its size varies depending on the volume of food present. For the purposes of gross description, the stomach can be divided into four regions: cardia, fundus, corpus (or body), and antrum (Fig. 22.1) (1,2). The superomedial margin is termed the lesser curvature, and the inferolateral margin is termed the greater curvature. The gastroesophageal junction (GEJ) is defined anatomically as the point where the tubular esopha- gus becomes the saccular stomach. It is present approximately 40 cm distal to the incisor teeth, although this distance varies depending on the height of the individual. Generally, this is the same level where the flat squamous esophageal mucosa is replaced by gastric mucosal folds (rugae). The cardia is found just distal to the lower end of the esophagus. It is a small and ill-defined area, extending 1 to 3 cm from the GEJ. The fundus is the portion of the stomach that lies above the GEJ, just below the left hemidiaphragm. The antrum com- prises the distal third of the stomach, proximal to the pyloric sphincter (pylorus), with the remainder of the stomach referred to as the corpus (body). Since they have the same type of mucosa, some authors do not distinguish between the corpus and the fundus and designate both these parts of the stomach as fundus. This is acceptable when discussing

EMBRYOLOGY AND POSTNATAL DEVELOPMENT

The stomach develops as a fusiform dilatation of the foregut caudal to the esophagus. This occurs first when the embryo is 7 mm in length. Initially, it is attached to the back of the abdomen by the dorsal mesogastrium and to the septum transversum (diaphragm) by the ventral mesogastrium. As the stomach enlarges, the dorsal mesogastrium becomes the greater omentum and the ventral mesogastrium becomes the lesser omentum. The stomach is derived from endoderm, and early glan- dular differentiation of the mucosal lining occurs first at the 80-mm stage of fetal development. Enzyme and acid production first occur at the 4th month of fetal life and are well established by the time of birth. The newborn stomach is fully developed and similar to that of the adult.

GROSS MORPHOLOGIC FEATURES The stomach is a flattened J-shaped organ located in the left upper quadrant of the abdomen. At its upper end, it joins

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